Metal foil back molding
Metal foil back injection is a special injection molding process in which a metal foil is embossed and bonded to plastic using an adhesion promoter . The metal foil with a thickness of up to 0.3 mm is inserted into the injection mold , back-injected with plastic and embossed so that a plastic part with a metal coating is created.
application
Hybrid technology is used to combine the advantages of metal and plastic in one molded part by means of a composite construction. The combination of these materials is also suitable for decorative applications in order to achieve a price and weight reduction compared to traditional technologies .
To increase the market attractiveness of products, for example from the electrical, small electrical, household or automotive industries , the trend is increasingly towards individual design and more exclusivity. Metallic surfaces play a major role here, so that the overmolding of metal foils is becoming increasingly important. The metal foils form the surface of the component and give the look and feel of metal. The plastic forms the substructure. The injection molding process makes it possible to integrate functions and processes, such as the introduction of snap hooks or fastening domes. Since the metal foils are very thin, tool surface structures can be molded onto the molded part surface at the same time using the injection pressure. This results in new design options.
procedure
First, the metal foil has to be cut to size and provided with an adhesive system . The film is then placed in the tool and closed. The plastic then injected behind the film presses it into the cavity . This is followed by an embossing process by the tool part behind the foil, whereby the foil completely takes on the contour of the tool. After demolding, the edge of the film must be removed if it was not already punched out during embossing .
The method can thus be viewed as a combination of back injection and injection compression molding or a variant of source flow compression molding .
Metal foil
The metal foil is used in a thickness of 0.1 mm to 0.3 mm, depending on the application. If the foil is thinner than 0.1 mm, the cool-touch effect can no longer be achieved as desired and larger deformations lead to tearing of the metal foil. If a film thicker than 0.3 mm is used, fine impressions, especially with stainless steel, can hardly be made. In principle, it is also true that much greater degrees of deformation can be achieved with stainless steel , since the elongation at break is more than twice as great. Depending on the film supplier, the metal film can be obtained with an adhesive system and / or protective film.
Detention system
Adhesion promoters enable the bond between metal foil and plastics that do not form a sufficiently strong bond with metals. Adhesive lacquers or adhesive foils are mostly used as adhesion promoters.
literature
- Frank Ehrig, Mario Studer, Matthias Holzinger, Hans-Rudolf Wey: Decorative components by back-molding metal foils . In: VDI Wissensforum IWB GmbH and VDI-Gesellschaft Kunststofftechnik (Hrsg.): VDI-Kunststoffband . 4283, injection molding 2007. VDI Verlag, Düsseldorf 2007 ( hsr.ch [PDF]).